The World’s Best Slime!
This is a very durable, stretchy type of slime that can withstand a great deal of abuse. It is a great stress reliever and can provide you with many hours of relaxing fun!
Safety precautions for all these methods: Adult supervision is required. This slime should not be tasted or eaten. Keep it away from young children and pets. Borax is toxic and irritating to the skin and eyes. Wear safety goggles. Exercise caution with boiling water.
What you need:
- Elmer’s All-Purpose white glue
- 20 Mule Team Borax (available in grocery stores, in the laundry department)
- Food coloring (optional)
- Zip-lock storage or freezer bag
- 2-Liter bottle
- Popsicle stick for stirring
- Disposable plastic cups
- Narrow-mouthed glass bottle (a Snapple iced tea bottle is ideal)
- Microwave oven or other heat source
- Microwave-safe container or beaker
- Permanent marker
- Water-based marker
- Eye dropper
What to do:
- Pour 60 mL (1/4 cup) of glue into a plastic cup.
- Add 60 mL (1/4 cup) of water to the glue and stir thoroughly. You now have a 50:50 glue-water mixture. You can make as much or as little slime as you desire, as long as you maintain the 50:50 ratio between glue and water.
- Add a few drops of food coloring, if desired, and stir thoroughly.
- Remove the label from an empty 2-Liter bottle and prominently label as “Borax”. Add 120 mL (1/2 cup ) of borax powder to the bottle. Fill halfway with water, and shake vigorously for several minutes. This will form a saturated borax solution. All of the borax will not dissolve right away, but most will dissolve over time. You can use the solution even if all of the solid has not dissolved.
- Pour 45 mL (3 tbsp) of the borax solution into an empty cup. Using your eyedropper, add this solution a little at a time to the glue-water mixture. The slime will collect on your stick as you stir. It is important that you not add too much borax solution, or the slime will become too stiff. A good rule of thumb is to stop adding borax when there is still a little fluid left in the bottom of the cup. This way, you will avoid adding too much borax.
- Remove the slime from the stick with your fingers, rinse off the water, and then work it with your hands.
What to do with it:
- Attempt to pull the slime apart slowly. What happens?
- Now attempt to pull the slime apart rapidly. What happens?
- Try to bounce it on the floor. Are you successful?
- Poke it quickly with your finger. What happens?
- Try to determine if your slime is a solid or a liquid. If left on the table, what happens to its shape? If your slime assumes the shape of its container, does this make it a solid or a liquid?
- Cut off the bottom half of a 2-Liter soda bottle and invert it so it acts like a funnel. Prop it up between two stacks of books so it is directly over a cup. Place the slime in the funnel and record the time it takes to reach the cup. Is the flow rate a good indicator of viscosity? Try varying the recipe to see how this affects the flow rate.
- Place your slime on a newspaper and then press down firmly. (This works best with non-colored slime). Is the newsprint transferred to the slime? Repeat with other types of print, such as a photocopy. Is the toner transferred? Test a page from an inkjet printer, and then try a page from a laser printer. What happens?
- Write on a piece of paper with a permanent marker. Press the slime down on the writing. (This works best with non-colored slime). Is the ink transferred to the slime? Repeat with a water-based marker. What happens?
- You can design your own colorful slime by drawing on it with markers or paint. Experiment to see what gives you the best results.
- To demonstrate the fluid-like properties of your slime, try this: Fill a Snapple bottle (or any narrow-mouthed glass bottle) to the brim with boiling water. Using a potholder to hold the bottle, pour out the boiling water. Quickly place a ball of slime on top of the bottle. Press it down a little so it makes a tight seal. Plunge the bottle into a bowl of cold water and observe the slime. It appears to get “sucked into the bottle!
- Try blowing slime bubbles! Wrap the slime around the end of a straw, then blow gently and slowly through the other end. It is important that an airtight seal be made between the slime and the straw. With practice, you can blow slime bubbles the size of a basketball!
- Store the slime in a zip-lock bag.
The science behind the slime:
Elmer’s glue is mainly composed of a polymer called polyvinyl acetate. (A “polymer” is basically just a long chain of molecules). Elmer’s glue has a greater viscosity (resistance to flow) than many liquids, but is not nearly as viscous as slime. The borax solution causes polyvinyl acetate molecules to “cross-link”.
You can compare “cross-linking” to spaghetti. After you’ve cooked a batch of spaghetti, it will start to dry if you leave it out for a while. Then, as the water evaporates you will start to see the spaghetti strands stick to each other (see Figure 2). Similarly, the borax (sodium tetraborate) molecules dissolve in water to produce borate ions, which act like the “joints” you see in Figure 2. In this case, however, the ions hold together “spaghetti” strands of polyvinyl acetate molecules. This makes for a much more viscous solution, (unlike the Elmer’s glue represented in Figure 1), since the polyvinyl acetate molecules are now linked firmly together by the borate ions.
Slime is an example of a non-Newtonian fluid. According to Isaac Newton, the viscosity of a liquid is dependent only on its temperature. But the viscosity of a non-Newtonian fluid, such as slime, can be altered in several other ways besides changing its temperature. If you pull the slime slowly apart, it will form long thin strands. But if pulled apart rapidly, it breaks. It can bounce somewhat if formed into a ball and dropped on a hard surface. If poked quickly with a finger, the finger will bounce off. But if poked slowly, the slime can easily absorb your finger. Other examples of non-Newtonian fluids are quicksand and Silly Putty.
Since the slime will assume the shape of its container, it is considered to be a liquid, not a solid. Solids have a definite shape; liquids do not. However, the slime is a very slow-flowing liquid, which is classified as one having a high degree of viscosity.
Water-based ink will tend to be more easily transferred to the slime than permanent ink. Water-based ink will also tend to run when used to draw on slime, but permanent ink will tend to make a more lasting impression.
When the bottle full of boiling water is emptied, the air within the bottle is heated. As air is heated, it expands. This expansion of hot air forces some of the air out of the bottle. When the bottle is cooled, the air within the bottle is cooled as well. When air cools, it contracts. Since some of the air was forced out of the bottle earlier, after cooling there is now less air pressure inside the bottle than there is outside the bottle. As a result, the slime is pushed into the bottle by this greater outside air pressure. It is important to note that the slime was pushed into the bottle, not sucked – remember, science never sucks! This experiment vividly demonstrates that slime is a liquid, which can be molded to fit into its container.